Well, these are id attributes you are showing:
<div id="span3 span49">
<div id="span3 span39">
In this case, you can use:
soup.find_all("div", id=lambda value: value and value.startswith("span3"))
Or:
soup.find_all("div", id=re.compile("^span3"))
If this was just a typo, and you actually have class attributes start with span3, and your really need to check the class to start with span3, you can use the “starts-with” CSS selector:
soup.select("div[class^=span3]")
This is because you cannot check the class attribute the same way you checked the id attribute because class is special, it is a multi-valued attribute.